Investors Expect too Much of Salix

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NEW YORK (TheStreet) -- It's become cliched to talk about Wall Street's hatred for uncertainty. But that's only when it's convenient. The Street also shamelessly discriminate with what it chooses to fear and/or ignore. In the case of specialty drug company Salix Pharmaceuticals , whose stock is up 115% in the trailing twelve months, there's no question the Street cares very little about the risks that still surrounds this company.

While Salix continues to be an incredible growth story, the company is marred in a battle with the Food and Drug Administration over a recent rejection of a subcutaneous form (injection) of key drug Relistor, which is used to treat constipation -- the type caused by pain medicines called opioids. While Salix has filed an appeal to the rejection, a response won't be issued by the FDA until March 2014.

Plus, there's also the risk associated with the company's rifamycin-based antibiotic drug Xifaxan, which is used to treat (among other things) irritable bowel syndrome and poor liver conditions. Although Xifaxan is posting some gaudy numbers, including 20% growth in the third quarter, the fact that this one drug accounts for 70% of Salix's total revenue is -- as I see it -- cause for some anxiety.

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I will grant that Salix is not alone when it comes to this sort of "product overreliance." Although companies strive for better diversification, very rarely is it ever achieved in Big Pharma. AbbVie , which I discussed recently, takes in 60% of its global revenue from rheumatoid arthritis drug Humira. The same goes for Johnson & Johnson , whose cancer drug Zytiga does all of the heavy lifting -- growing in the recent quarter by 70% year over year.

But unlike Johnson & Johnson, which also has strong devices business, not to mention growing segments like nutrition and orthopedics, Salix still has to prove the lasting power of Xifaxan, which is still in Phase III research for IBS. What this means is that not only does Salix have to rely on positive data during the study, but that data has to be convincing enough for the FDA to grant approval. And this is while the company waits on appeal response for the Relistor.